(Image credit- Electrek)
With the development of new battery chemistry, a creative solution to the problems experienced by owners of electric vehicles in cold climates has been found.
Electric vehicle battery issues
Due to the liquid electrolyte, the current lithium-ion batteries have a severe challenge in freezing conditions.
This vital battery component makes it easier for the ions, which transport the charge, to move between the two electrodes, allowing the battery to charge and discharge.
However, the liquid electrolyte freezes at below-freezing temperatures, drastically reducing the efficiency of charging electric vehicles in cold climates.
To address this problem, a group of researchers from the Argonne and Lawrence Berkeley National Laboratories of the US Department of Energy developed an electrolyte that contains fluorine and performs admirably even in extremely cold temperatures.
The finding offers a glimmer of hope for the use of this low-temperature electrolyte in electronics like computers and phones as well as in electric grid energy storage and not just in batteries for electric vehicles.
Senior chemist and group leader Zhengcheng “John” Zhang from the Chemical Sciences and Engineering division of Argonne National Laboratory described their team’s accomplishment by saying, “Our team not only found an antifreeze electrolyte whose charging performance does not decline at minus 4 degrees Fahrenheit, but we also discovered, at the atomic level, what makes it so effective.”
The electrolyte used in current lithium-ion batteries is made up of an easily available salt called lithium hexafluorophosphate as well as carbonate solvents like ethylene carbonate. These solvents cause the salt to dissolve, creating a liquid medium as a result.
Lithium ions are moved from the cathode to the anode during charging by the liquid electrolyte, which is encircled by clusters of solvent molecules.
The solid-electrolyte interphase, which is formed by these clusters and allows only lithium ions to pass through, allows the anode to store lithium atoms for use in electrical energy production during discharge.
On the anode surface during initial charging, clusters create a protective solid-electrolyte interphase that serves as a filter for lithium ions while obstructing solvent molecules. As a result, the anode can store lithium atoms in the graphite structure for later discharge to produce energy.
However, due to high ion-solvent cluster interaction, freezing of the electrolyte with carbonate solvents in cold temperatures prevents the transfer of lithium ions to the anode.
The most effective mixture for releasing lithium ions in below-freezing temperatures was discovered after the researchers investigated a number of fluorine-containing solvents. They also identified the atomic-level elements that influenced its efficiency.
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The team’s fluorinated electrolyte demonstrated consistent energy storage capacity over 400 charge-discharge cycles in laboratory tests at minus 4 degrees Fahrenheit, which is comparable to a cell employing a typical carbonate-based electrolyte at ambient temperature.
According to Zhang, the study showed how to modify electrolyte solvents for extremely cold temperatures.
The team further asserts that because the antifreeze electrolyte is not flammable, it is safer than conventional carbonate-based electrolytes. Additionally, they are looking for an industrial partner to adopt the low-temperature, safer electrolyte while simultaneously patenting it.